1. Field
Embodiments of the invention relate to methods for crosslinking nanoparticles and coated substrates made according to the methods. Crosslinked nanoparticles on substrates can be used in electrochromic devices and/or photovoltaic devices.
2. Technical Background
Forming layers of particles, for example, nanoparticles that adhere to each other and/or to a substrate is useful for several applications such as in the production of photovoltaic devices such as solar cells. In some conventional solar cell applications, inorganic oxide particle layers are formed, which are subsequently sintered, or otherwise caused to stick together and to the substrate. Typically a high temperature sintering or a pseudo-sintering process is used to form a porous layer of the particles.
Some particles such as anatase titania cannot be fully sintered without the titania changing phase from anatase to rutile at high temperatures, for example, temperatures of 915° C. or above. Thus, anatase titania is usually pseudo-sintered, below its melting point, in order to minimize this phase change, since it can cause a reduction in surface area of the titania. However, conventional pseudo-sintering methods utilize relatively high temperatures, for example, temperatures greater than 300° C. or 450° C.
Temperatures greater than 300° C. or 450° C. can render pseudo-sintering incompatible with many substrate materials, for example, organic substrates, since the elevated temperatures can cause degradation in the organic substrates.
It would be advantageous to have a method for crosslinking nanoparticles at low temperatures (below 300° C.), which is compatible with nanoparticles and/or substrates not able to withstand high temperatures, and/or capable of using crosslinkers having an increased reactivity.